Electrode bonding methods for loading various types of parts, such as a semiconductor device having bump electrodes or flat electrodes and a part having a flexible substrate equipped with bump electrodes or flat electrodes, on substrates that have flat electrodes or bump electrodes, and bonding those electrodes to each other by ultrasonic bonding or thermocompression bonding have heretofore been known. If the ultrasonic bonding or thermocompression bonding is performed with oxide films on the electrode surfaces or in the presence of organic stains and absorbed moisture, the bonding surfaces can involve those to cause a lack of bonding force. Thus, it has also been known that the surfaces of the electrodes of the parts and substrates are wet-cleaned for acid treatment or cleaned by plasma processing in a vacuum processing chamber, thereby removing oxide films from the electrode surfaces or removing organic stains to provide a bonding state of high bonding force and reliability.
Cleaning apparatuses for performing the cleaning typically require large-scale devices and cost high, however, and the cleaning apparatuses are installed away from mounting apparatuses which load and bond the parts onto the substrates. There has thus been the problem that while the substrates and parts are transported therebetween, oxide films, organic stains, and moisture absorption can occur again from moisture, oxygen, carbon dioxide, and the like in the air with a drop in bonding force.
Then, as a bonding method for solving this problem, there has been known a bonding method which comprises the steps, such as shown in FIGS. 10A to 10C, of: putting a bonding article (electronic part) 61 and a to-be-bonded article (substrate) 62 close to each other with their flat surfaces maintained generally in parallel, supplying inert gas 64 from a gas nozzle 63 to therebetween so that the gap is filled with the inert gas, and applying electric power from a power supply 65 to between the bonding article 61 and the to-be-bonded article 62 to generate plasma 66 (FIG. 10A); then stopping the supply of power to extinguish the plasma 66 (FIG. 10B); and then putting the bonding article 61 into contact with the to-be-bonded article 62 for bonding (FIG. 10C) (See Japanese Patent Laid-Open Publication No. 2004-223600).
As shown in FIG. 11, there has also been known a method which comprises: supplying a mixed gas of an inert gas and a reactive gas from a gas source 71 through flow rate adjusting means 72 to atmospheric pressure plasma generating means 73; applying a high frequency electric field to the mixed gas in the atmospheric pressure plasma generating means 73 to generate atmospheric pressure plasma 74; and spraying the generated atmospheric pressure plasma 74 from a plasma nozzle 75 to bonding areas of a bonding article (electronic part) 76 and a to-be-bonded article (substrate) 77 to clean the surfaces of the bonding areas with the plasma while bringing the clean bonding areas of the bonding article 76 and the to-be-bonded article 77 into contact with each other in a bonding apparatus 78 to bond the bonding article 76 and the to-be-bonded article 77 (See Japanese Patent Laid-Open Publication No. 2004-228346).
By the way, in the bonding method shown in FIGS. 10A to 10C, electric power is supplied from the power supply 65 to between the bonding article 61 and the to-be-bonded article 62 to generate the plasma 66 therebetween, and it follows that the highly-charged plasma 66 lies between the bonding article 61 and the to-be-bonded article 62. This leads to the problem that if the bonding article 61 is a semiconductor device with electrodes, there is the possibility of damaging the bonding article 61 itself by charging up or the like, with a drop in the quality level of the bonding article 61 itself.
Moreover, in the configuration shown in FIG. 11, the atmospheric pressure plasma 74 generated by the atmospheric pressure plasma generating means 73 has only a short life and attenuates sharply once outside the atmospheric pressure plasma generating means 73. This requires a short distance between the atmospheric pressure plasma generating means 73 and the plasma nozzle 75. In actual apparatuses, it is difficult to practice such a mode as shown in FIG. 11 because of layout spaces of the individual instruments. There is also the problem that the atmospheric pressure plasma 74 coming into the air from the plasma nozzle 75 collides with moisture and oxygen contained in the air and disappears, and it is known that the effective irradiation range of the atmospheric pressure plasma 74 from the plasma nozzle 75 is within 3 mm from the extremity of the plasma nozzle 75. In the meantime, as shown in FIG. 12, the area where electrodes 76a of a bonding article (electronic part) 76 and electrodes 77a of a to-be-bonded article (substrate) 77 are formed ranges several millimeters if the bonding article (electronic part) 76 is small, and several tens of millimeters if the bonding article (electronic part) 76 is large. In such circumstances, there is a problem since in many cases the surfaces of the electrodes 76a to be irradiated with the atmospheric pressure plasma 74 fail to be irradiated as in area A, and the surfaces of the electrodes 76a to be irradiated can no longer benefit from the plasma effect even if irradiated successfully as in area B.
The present invention has been devised to solve the foregoing conventional problems, and it is an object thereof to provide an electrode bonding method which has no possibility of damaging a part to be bonded to a substrate, is capable of plasma-cleaning electrode surfaces even if the part has a large electrode layout area, and is further capable of maintaining the cleaned state while bonding the electrodes to provide a bonding state of high bonding force and high reliability.
Another object is to provide a part mounting apparatus to which the foregoing electrode bonding method is applied to provide a bonding state of high bonding force and high reliability.